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Understanding the Immune System
Adapted by Mary
Shomon
The most common types of allergic reactions-hay fever, some kinds of asthma, and hives-are produced when the immune system response to a false alarm. In a susceptible person, a normally harmless substance-grass pollen or house dust, for example-is perceived as a threat and is attacked.
Such allergic reactions are related to the antibody known as immunoglobulin E. Like other antibodies, each IgE antibody is specific; one reacts against oak pollen, another against ragweed. The role of IgE in the natural order is not known, although some scientists suspect that it developed as a defense against infection by parasitic worms.
The first time an allergy-prone person is exposed to an allergen, he or she makes large amounts of the corresponding IgE antibody. These IgE molecules attach to the surfaces of mast cells (in tissue) or basophils (in the circulation). Mast cells are plentiful in the lungs, skin, tongue, and linings of the nose and intestinal tract.
